Hypothermia

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Chapter 67 Hypothermia

Howard M. Corneli, MD

1 Why are children more prone to hypothermia than adults?

Children have larger body surface–to–mass ratios.

They may have less insulation, faster metabolism, and smaller energy reserves.

They may be more at risk for medical illness, trauma, or environmental exposure.

2 Does hypothermia require severe cold exposure?

No. Unfortunately, clinicians may suspect hypothermia only when severe environmental exposure is evident. Any immersion in warm or cold water, or any major illness or trauma, may precipitate hypothermia. It is also seen in conditions as diverse as sepsis, hypoglycemia, drug ingestion, and child abuse, any of which may be occult.

Children are more at risk than adults for iatrogenic hypothermia due to rescue, transport, and resuscitation.

3 Why is hypothermia overlooked in pediatric patients in the emergency department (ED)?

Hypothermia victims only appear cold in the mild range of hypothermia. In deeper hypothermia, signs such as shivering, pallor, cyanosis, and agitation are replaced by flushing, edema, muscular rigidity, and decreased mental status. Standard clinical thermometers only measure down to 94° F (34° C).

4 What are some risk factors for hypothermia?

Trauma	Rescue
Severe illness	Transport
Immersion or submersion	Resuscitation
Exposure to wind or cold air	Intoxication, especially with:
Central nervous system illness or injury	Alcohol
Hypothalamic dysfunction	Barbiturates
Endocrine impairment	Phenothiazines
Metabolic impairment	Burns and weeping dermatoses
Iatrogenic causes	Child abuse (e.g., cold water baths)

5 What clinical clues should prompt measurement of core temperature?

Any of the above risk factors (including, but not limited to, any critical care patient)

Decreased mental status, respiration, or circulation without other obvious cause

A J (Osborne) wave on electrocardiogram (Fig. 67-1) is diagnostic when present, but is seen in only about 10–80% of cases in various series.

Figure 67-1 EKG showing Osborne or J wave.

Nolan J, Soar J: Images in resuscitation: The ECG in hypothermia. Resuscitation 64:133, 2005.

6 How should temperatures be taken to detect hypothermia?

A low-reading thermometer must be used. Oral and axillary temperatures are unreliable. Rectal temperatures are subject to damping, artifact, and time lags up to 1 hour. If used, rectal temperatures must be taken deep in the rectum for at least several minutes. The reliability of tympanic temperatures in the setting of significant hypothermia has not been established. Temperature probes in the bladder, esophagus, or nasopharynx are typically used to provide core temperatures of the trunk.

Danzl DF, Pozos RS: Accidental hypothermia. N Engl J Med 331:1756, 1994.

7 Define mild, moderate, and severe hypothermia

Mild hypothermia: Temperature ranges from approximately 32° to 35° C. In this range, the body attempts to combat heat loss by shivering, increasing metabolism and vasoconstriction.

Moderate hypothermia: Temperature spans the range from 28° to 32° C. In this range, compensatory mechanisms begin to fail, and mental status may be altered.

Severe hypothermia: Temperature (< 28° C) leads to failed thermoregulation, metabolic shutdown, and paradoxical vasodilatation accompanied by hypovolemia, decreased perfusion, and stupor or coma.

Corneli HM: Hot topics in cold medicine: Controversies in accidental hypothermia. Clin Pediatr Emerg Med 2:179–191, 2001.

8 Describe some landmarks for converting between Celsius and Fahrenheit

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